HR: 0800h
AN: T11D-1311    [Abstracts]
TI: Coseimic and postseismic deformation of Chengkung Earthquake in Eastern Taiwan Revealed by Strong Motion and GPS Data
AU: * Hu, J
EM: jchu@ntu.edu.tw
AF: Department of Geosciences, Natioanl Taiwan University, No. 1, Sec. 4, Roosevelt Road,, Taipei, 106 Taiwan
AU: Cheng, L
EM: r92224106@ntu.edu.tw
AF: Department of Geosciences, Natioanl Taiwan University, No. 1, Sec. 4, Roosevelt Road,, Taipei, 106 Taiwan
AU: Wu, Y
EM: drymwu@ntu.edu.tw
AF: Department of Geosciences, Natioanl Taiwan University, No. 1, Sec. 4, Roosevelt Road,, Taipei, 106 Taiwan
AU: Rau, R
EM: raurj@mail.ncku.edu.tw
AF: Department of Earth Sciences, National Cheng Kung University, No.1, Ta-Hsueh Road, Tainan, 701 Taiwan
AU: Lee, J
EM: jclee@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, No. 128, Sec. 2, Academia Road, Taipei, 115 Taiwan
AB: The Mw 6.5 Chengkung Earthquake occurred on December 10th, 2003 in the Costal Range of eastern Taiwan is believed to rupture the NNE-striking Chihshang fault in the Longitudinal Valley. The Chihshang fault is the most active creeping segment of the Longitudinal Valley fault, which is considered as a plate suture zone between the Luzon arc of the Philippine Sea plate and the Chinese continental margin of the Eurasian plate. Based on the relocation of aftershock sequences, the main shock is a pure thrust event that ruptures the east dipping Chihshang fault plane. All the stations in the hanging wall show significant uplift. The maximum permanent vertical displacement shown by strong motion data in the hanging wall side is about 19 cm, meanwhile the horizontal displacement is about 9 cm trending NE. In general the coseismic horizontal displacement shows a fan-shape pattern. It is worthy to notice that the some stations on the footwall of the Chihshang fault were uplifted during this earthquake event. For characterizing the coseismic pattern, we use 40 strong motion and 6 continuous GPS data around the Chihshang fault to simulate the subsurface fault geometry and the distribution of coseismic slip along the fault surface by 3-D dislocation model. The results show that the model containing only single Chihshang fault can not well fit the vertical displacement on the footwall side. Thus we try to reinvestigate the coseismic displacement by adding an additional subfault plane appended under the Longitudinal Valley. Due to this subfault geometry, additional rupture surface will locate at a distance of 3.5 km away from Chihshang fault trace. The predicted coseismic displacemet by inversion of the two fault geometry model is much better than that of single fault model, especially around the Longitudinal Valley. The best-fitted model reveals that the maximal dislocation is about 1m dip-slip on the Chihshang fault plane near the hypocenter, and the dislocations near the surface are partly locked and decline to about 1~10 cm on both fault planes. The calculated scalar moment is 1.9E26 dyne-cm, which is quite compatible with the 2.0E26 dyne-cm based on the result of Harvard CMT.
DE: 7230 Seismicity and seismotectonics
DE: 3210 Modeling
DE: 1206 Crustal movements--interplate (8155)
DE: 1242 Seismic deformations (7205)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting